1. Field of the Invention
The invention relates to an objective lens driving device and an optical pickup apparatus including the same. Particularly, the invention relates to: an objective lens driving device including a constitution for strengthening effective magnetic fluxes of magnets included in an actuator frame; and an optical pickup apparatus including the same.
2. Description of the Related Art
In an objective lens driving device in an optical head for optically reading or writing a signal from or to an optical disc, an objective lens holder (hereinafter referred to as an “OBL holder”) to which an objective lens is attached is supported to be movable relative to an actuator frame. In addition, a focus coil and tracking coils, as well as tilt coils depending on the necessity, are mounted on the OBL holder; the effective areas of these driving coils are placed within predetermined magnetic fields formed by magnetic circuits; and thereby, the objective lens is driven in accordance with signals supplied to the driving coils.
The structure of an existing objective lens driving device is shown, for example, in Japanese Patent Application Publication No. 2005-302161 (JP2005-302161A). Referring to FIG. 3 of this document, a focusing coil 25 and tracking coils 26 are housed in a coil holder 24 shaped almost like a rectangular frame. In addition, an objective lens driving device 8 including the coil holder 24 is driven in a predetermined direction by the magnetic actions of the focusing coil 25 and the tracking coils 26. Furthermore, referring to FIG. 2 of JP2005-302161A, back yokes 28 are placed on the back side of tilt magnets 29, respectively.